Method and apparatus for dispersed storage data transfer

ABSTRACT

The method begins with a processing module determining whether to reconstruct data corresponding to a plurality of data slices when the plurality of data slices is to be transferred from a first type of memory device to a second type of memory device. The method continues with the processing module retrieving the plurality of data slices from a first set of memory devices that are of the first type of memory, reconstructing at least a portion of the data from the plurality of data slice in accordance with a first error coding dispersal function to produce reconstructed data, encoding the reconstructed data in accordance with a second error coding dispersal function to produce a second plurality of data slices, and storing the second plurality of data slices in a second set of memory devices that are of the second type of memory when the data is to be reconstructed.

CROSS REFERENCE To RELATED PATENTS

This patent application is claiming priority under 35 USC §119 to aprovisionally filed patent application entitled DISTRIBUTED STORAGENETWORK MEMORY UTILIZATION, having a provisional filing date of Sep. 30,2009, and a provisional Ser. No. 61/247,190.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates generally to computing systems and moreparticularly to data storage solutions within such computing systems.

2. Description of Related Art

Computers are known to communicate, process, and store data. Suchcomputers range from wireless smart phones to data centers that supportmillions of web searches, stock trades, or on-line purchases every day.In general, a computing system generates data and/or manipulates datafrom one form into another. For instance, an image sensor of thecomputing system generates raw picture data and, using an imagecompression program (e.g., JPEG, MPEG, etc.), the computing systemmanipulates the raw picture data into a standardized compressed image.

With continued advances in processing speed and communication speed,computers are capable of processing real time multimedia data forapplications ranging from simple voice communications to streaming highdefinition video. As such, general-purpose information appliances arereplacing purpose-built communications devices (e.g., a telephone). Forexample, smart phones can support telephony communications but they arealso capable of text messaging and accessing the internet to performfunctions including email, web browsing, remote applications access, andmedia communications (e.g., telephony voice, image transfer, musicfiles, video files, real time video streaming. etc.).

Each type of computer is constructed and operates in accordance with oneor more communication, processing, and storage standards. As a result ofstandardization and with advances in technology, more and moreinformation content is being converted into digital formats. Forexample, more digital cameras are now being sold than film cameras, thusproducing more digital pictures. As another example, web-basedprogramming is becoming an alternative to over the air televisionbroadcasts and/or cable broadcasts. As further examples, papers, books,video entertainment, home video, etc. are now being stored digitally,which increases the demand on the storage function of computers.

A typical computer storage system includes one or more memory devicesaligned with the needs of the various operational aspects of thecomputer's processing and communication functions. Generally, theimmediacy of access dictates what type of memory device is used. Forexample, random access memory (RAM) memory can be accessed in any randomorder with a constant response time, thus it is typically used for cachememory and main memory. By contrast, memory device technologies thatrequire physical movement such as magnetic disks, tapes, and opticaldiscs, have a variable response time as the physical movement can takelonger than the data transfer, thus they are typically used forsecondary memory (e.g., hard drive, backup memory, etc.).

A computer's storage system will be compliant with one or more computerstorage standards that include, but are not limited to, network filesystem (NFS), flash file system (FFS), disk file system (DFS), smallcomputer system interface (SCSI), internet small computer systeminterface (iSCSI), file transfer protocol (FTP), and web-baseddistributed authoring and versioning (WebDAV). These standards specifythe data storage format (e.g., files, data objects, data blocks,directories, etc.) and interfacing between the computer's processingfunction and its storage system, which is a primary function of thecomputer's memory controller.

Despite the standardization of the computer and its storage system,memory devices fail; especially commercial grade memory devices thatutilize technologies incorporating physical movement (e.g., a discdrive). For example, it is fairly common for a disc drive to routinelysuffer from bit level corruption and to completely fail after threeyears of use. One solution is to a higher-grade disc drive, which addssignificant cost to a computer.

Another solution is to utilize multiple levels of redundant disc drivesto replicate the data into two or more copies. One such redundant driveapproach is called redundant array of independent discs (RAID). In aRAID device, a RAID controller adds parity data to the original databefore storing it across the array. The parity data is calculated fromthe original data such that the failure of a disc will not result in theloss of the original data. For example,

RAID 5 uses three discs to protect data from the failure of a singledisc. The parity data, and associated redundancy overhead data, reducesthe storage capacity of three independent discs by one third (e.g.,n−1=capacity). RAID 6 can recover from a loss of two discs and requiresa minimum of four discs with a storage capacity of n−2.

While RAID addresses the memory device failure issue, it is not withoutits own failures issues that affect its effectiveness, efficiency andsecurity. For instance, as more discs are added to the array, theprobability of a disc failure increases, which increases the demand formaintenance. For example, when a disc fails, it needs to be manuallyreplaced before another disc fails and the data stored in the RAIDdevice is lost. To reduce the risk of data loss, data on a RAID deviceis typically copied on to one or more other RAID devices. While thisaddresses the loss of data issue, it raises a security issue sincemultiple copies of data are available, which increases the chances ofunauthorized access. Further, as the amount of data being stored grows,the overhead of RAID devices becomes a non-trivial efficiency issue.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a computingsystem in accordance with the invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the invention;

FIG. 3 is a schematic block diagram of an embodiment of a distributedstorage processing module in accordance with the invention;

FIG. 4 is a schematic block diagram of an embodiment of a grid module inaccordance with the invention;

FIG. 5 is a diagram of an example embodiment of error coded data slicecreation in accordance with the invention;

FIG. 6 is a schematic block diagram of another embodiment of a computingsystem in accordance with the invention;

FIG. 7 is a flowchart of an embodiment of a method for determining datadistribution in accordance with the present invention;

FIG. 8 is another flowchart of another embodiment of a method fordetermining data distribution in accordance with the present invention;

FIG. 9 is a schematic block diagram of an embodiment of a distributedstorage unit in accordance with the invention;

FIG. 10 is a flowchart of another embodiment of a method for determiningdata distribution in accordance with the present invention; and

FIG. 11 is a flowchart of an embodiment of a method for memory devicemanagement in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of a computing system 10 thatincludes one or more of a first type of user devices 12, one or more ofa second type of user devices 14, at least one distributed storage (DS)processing unit 16, at least one DS managing unit 18, at least onestorage integrity processing unit 20, and a distributed storage network(DSN) memory 22 coupled via a network 24. The network 24 may include oneor more wireless and/or wire lined communication systems; one or moreprivate intranet systems and/or public internet systems; and/or one ormore local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of distributed storage (DS) units36 for storing data of the system. Each of the DS units 36 includes aprocessing module and memory and may be located at a geographicallydifferent site than the other DS units (e.g., one in Chicago, one inMilwaukee, etc.). The processing module may be a single processingdevice or a plurality of processing devices. Such a processing devicemay be a microprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module may have an associatedmemory and/or memory element, which may be a single memory device, aplurality of memory devices, and/or embedded circuitry of the processingmodule. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, cache memory, and/or any device that storesdigital information. Note that if the processing module includes morethan one processing device, the processing devices may be centrallylocated (e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that when the processing module implements one or more ofits functions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory and/or memory element storing thecorresponding operational instructions may be embedded within, orexternal to, the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Still further notethat, the memory element stores, and the processing module executes,hard coded and/or operational instructions corresponding to at leastsome of the steps and/or functions illustrated in FIGS. 1-9.

Each of the user devices 12-14, the DS processing unit 16, the DSmanaging unit 18, and the storage integrity processing unit 20 may be aportable computing device (e.g., a social networking device, a gamingdevice, a cell phone, a smart phone, a personal digital assistant, adigital music player, a digital video player, a laptop computer, ahandheld computer, a video game controller, and/or any other portabledevice that includes a computing core) and/or a fixed computing device(e.g., a personal computer, a computer server, a cable set-top box, asatellite receiver, a television set, a printer, a fax machine, homeentertainment equipment, a video game console, and/or any type of homeor office computing equipment). Such a portable or fixed computingdevice includes a computing core 26 and one or more interfaces 30, 32,and/or 33. An embodiment of the computing core 26 will be described withreference to FIG. 2.

With respect to the interfaces, each of the interfaces 30, 32, and 33includes software and/or hardware to support one or more communicationlinks via the network 24 and/or directly. For example, interfaces 30support a communication link (wired, wireless, direct, via a LAN, viathe network 24, etc.) between the first type of user device 14 and theDS processing unit 16. As another example, DSN interface 32 supports aplurality of communication links via the network 24 between the DSNmemory 22 and the DS processing unit 16, the first type of user device12, and/or the storage integrity processing unit 20. As yet anotherexample, interface 33 supports a communication link between the DSmanaging unit 18 and any one of the other devices and/or units 12, 14,16, 20, and/or 22 via the network 24.

In general and with respect to data storage, the system 10 supportsthree primary functions: distributed network data storage management,distributed data storage and retrieval, and data storage integrityverification. In accordance with these three primary functions, data canbe distributedly stored in a plurality of physically different locationsand subsequently retrieved in a reliable and secure manner regardless offailures of individual storage devices, failures of network equipment,the duration of storage, the amount of data being stored, attempts athacking the data, etc.

The DS managing unit 18 performs distributed network data storagemanagement functions, which include establishing distributed datastorage parameters, performing network operations, performing networkadministration, and/or performing network maintenance. The DS managingunit 18 establishes the distributed data storage parameters (e.g.,allocation of virtual DSN memory space, distributed storage parameters,security parameters, billing information, user profile information,etc.) for one or more of the user devices 12-14 (e.g., established forindividual devices, established for a user group of devices, establishedfor public access by the user devices, etc.). For example, the DSmanaging unit 18 coordinates the creation of a vault (e.g., a virtualmemory block) within the DSN memory 22 for a user device (for a group ofdevices, or for public access). The DS managing unit 18 also determinesthe distributed data storage parameters for the vault. In particular,the DS managing unit 18 determines a number of slices (e.g., the numberthat a data segment of a data file and/or data block is partitioned intofor distributed storage) and a read threshold value (e.g., the minimumnumber of slices required to reconstruct the data segment).

As another example, the DS managing module 18 creates and stores,locally or within the DSN memory 22, user profile information. The userprofile information includes one or more of authentication information,permissions, and/or the security parameters. The security parameters mayinclude one or more of encryption/decryption scheme, one or moreencryption keys, key generation scheme, and data encoding/decodingscheme.

As yet another example, the DS managing unit 18 creates billinginformation for a particular user, user group, vault access, publicvault access, etc. For instance, the DS managing unit 18 tracks thenumber of times user accesses a private vault and/or public vaults,which can be used to generate a per-access bill. In another instance,the DS managing unit 18 tracks the amount of data stored and/orretrieved by a user device and/or a user group, which can be used togenerate a per-data-amount bill.

The DS managing unit 18 also performs network operations, networkadministration, and/or network maintenance. As at least part ofperforming the network operations and/or administration, the DS managingunit 18 monitors performance of the devices and/or units of the system10 for potential failures, determines the devices and/or unit'sactivation status, determines the devices' and/or units' loading, andany other system level operation that affects the performance level ofthe system 10. For example, the DS managing unit 18 receives andaggregates network management alarms, alerts, errors, statusinformation, performance information, and messages from the devices12-14 and/or the units 16, 20, 22. For example, the DS managing unit 18receives a simple network management protocol (SNMP) message regardingthe status of the DS processing unit 16.

The DS managing unit 18 performs the network maintenance by identifyingequipment within the system 10 that needs replacing, upgrading,repairing, and/or expanding. For example, the DS managing unit 18determines that the DSN memory 22 needs more DS units 36 or that one ormore of the DS units 36 needs updating.

The second primary function (i.e., distributed data storage andretrieval) begins and ends with a user device 12-14. For instance, if asecond type of user device 14 has a data file 38 and/or data block 40 tostore in the DSN memory 22, it send the data file 38 and/or data block40 to the DS processing unit 16 via its interface 30. As will bedescribed in greater detail with reference to FIG. 2, the interface 30functions to mimic a conventional operating system (OS) file systeminterface (e.g., network file system (NFS), flash file system (FFS),disk file system (DFS), file transfer protocol (FTP), web-baseddistributed authoring and versioning (WebDAV), etc.) and/or a blockmemory interface (e.g., small computer system interface (SCSI), internetsmall computer system interface (iSCSI), etc.). In addition, theinterface 30 may attach a user identification code (ID) to the data file38 and/or data block 40.

The DS processing unit 16 receives the data file 38 and/or data block 40via its interface 30 and performs a distributed storage (DS) process 34thereon (e.g., an error coding dispersal storage function). The DSprocessing 34 begins by partitioning the data file 38 and/or data block40 into one or more data segments, which is represented as Y datasegments. For example, the DS processing 34 may partition the data file38 and/or data block 40 into a fixed byte size segment (e.g., 2¹ to2^(n) bytes, where n=>2) or a variable byte size (e.g., change byte sizefrom segment to segment, or from groups of segments to groups ofsegments, etc.).

For each of the Y data segments, the DS processing 34 error encodes(e.g., forward error correction (FEC), information dispersal algorithm,or error correction coding) and slices (or slices then error encodes)the data segment into a plurality of error coded (EC) data slices 42-48,which is represented as X slices per data segment. The number of slices(X) per segment, which corresponds to a number of pillars n, is set inaccordance with the distributed data storage parameters and the errorcoding scheme. For example, if a Reed-Solomon (or other FEC scheme) isused in an n/k system, then a data segment is divided into n slices,where k number of slices is needed to reconstruct the original data(i.e., k is the threshold). As a few specific examples, the n/k factormay be 5/3; 6/4; 8/6; 8/5; 16/10.

For each slice 42-48, the DS processing unit 16 creates a unique slicename and appends it to the corresponding slice 42-48. The slice nameincludes universal DSN memory addressing routing information (e.g.,virtual memory addresses in the DSN memory 22) and user-specificinformation (e.g., user ID, file name, data block identifier, etc.).

The DS processing unit 16 transmits the plurality of EC slices 42-48 toa plurality of DS units 36 of the DSN memory 22 via the DSN interface 32and the network 24. The DSN interface 32 formats each of the slices fortransmission via the network 24. For example, the DSN interface 32 mayutilize an internet protocol (e.g., TCP/IP, etc.) to packetize theslices 42-48 for transmission via the network 24.

The number of DS units 36 receiving the slices 42-48 is dependent on thedistributed data storage parameters established by the DS managing unit18. For example, the DS managing unit 18 may indicate that each slice isto be stored in a different DS unit 36. As another example, the DSmanaging unit 18 may indicate that like slice numbers of different datasegments are to be stored in the same DS unit 36. For example, the firstslice of each of the data segments is to be stored in a first DS unit36, the second slice of each of the data segments is to be stored in asecond DS unit 36, etc. In this manner, the data is encoded anddistributedly stored at physically diverse locations to improved datastorage integrity and security. Further examples of encoding the datasegments will be provided with reference to one or more of FIGS. 2-9.

Each DS unit 36 that receives a slice 42-48 for storage translates thevirtual DSN memory address of the slice into a local physical addressfor storage. Accordingly, each DS unit 36 maintains a virtual tophysical memory mapping to assist in the storage and retrieval of data.

The first type of user device 12 performs a similar function to storedata in the DSN memory 22 with the exception that it includes the DSprocessing. As such, the device 12 encodes and slices the data fileand/or data block it has to store. The device then transmits the slices35 to the DSN memory via its DSN interface 32 and the network 24.

For a second type of user device 14 to retrieve a data file or datablock from memory, it issues a read command via its interface 30 to theDS processing unit 16. The DS processing unit 16 performs the DSprocessing 34 to identify the DS units 36 storing the slices of the datafile and/or data block based on the read command. The DS processing unit16 may also communicate with the DS managing unit 18 to verify that theuser device 14 is authorized to access the requested data.

Assuming that the user device is authorized to access the requesteddata, the DS processing unit 16 issues slice read commands to at least athreshold number of the DS units 36 storing the requested data (e.g., toat least 10 DS units for a 16/10 error coding scheme). Each of the DSunits 36 receiving the slice read command, verifies the command,accesses its virtual to physical memory mapping, retrieves the requestedslice, or slices, and transmits it to the DS processing unit 16.

Once the DS processing unit 16 has received a read threshold number ofslices for a data segment, it performs an error decoding function andde-slicing to reconstruct the data segment. When Y number of datasegments has been reconstructed, the DS processing unit 16 provides thedata file 38 and/or data block 40 to the user device 14. Note that thefirst type of user device 12 performs a similar process to retrieve adata file and/or data block.

The storage integrity processing unit 20 performs the third primaryfunction of data storage integrity verification. In general, the storageintegrity processing unit 20 periodically retrieves slices 45, and/orslice names, of a data file or data block of a user device to verifythat one or more slices have not been corrupted or lost (e.g., the DSunit failed). The retrieval process mimics the read process previouslydescribed.

If the storage integrity processing unit 20 determines that one or moreslices is corrupted or lost, it rebuilds the corrupted or lost slice(s)in accordance with the error coding scheme. The storage integrityprocessing unit 20 stores the rebuild slice, or slices, in theappropriate DS unit(s) 36 in a manner that mimics the write processpreviously described.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,at least one IO device interface module 62, a read only memory (ROM)basic input output system (BIOS) 64, and one or more memory interfacemodules. The memory interface module(s) includes one or more of auniversal serial bus (USB) interface module 66, a host bus adapter (HBA)interface module 68, a network interface module 70, a flash interfacemodule 72, a hard drive interface module 74, and a DSN interface module76. Note the DSN interface module 76 and/or the network interface module70 may function as the interface 30 of the user device 14 of FIG. 1.Further note that the IO device interface module 62 and/or the memoryinterface modules may be collectively or individually referred to as IOports.

The processing module 50 may be a single processing device or aplurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module 50 may have anassociated memory and/or memory element, which may be a single memorydevice, a plurality of memory devices, and/or embedded circuitry of theprocessing module 50. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module 50includes more than one processing device, the processing devices may becentrally located (e.g., directly coupled together via a wired and/orwireless bus structure) or may be distributedly located (e.g., cloudcomputing via indirect coupling via a local area network and/or a widearea network). Further note that when the processing module 50implements one or more of its functions via a state machine, analogcircuitry, digital circuitry, and/or logic circuitry, the memory and/ormemory element storing the corresponding operational instructions may beembedded within, or external to, the circuitry comprising the statemachine, analog circuitry, digital circuitry, and/or logic circuitry.Still further note that, the memory element stores, and the processingmodule 50 executes, hard coded and/or operational instructionscorresponding to at least some of the steps and/or functions illustratedin FIGS. 1-9.

FIG. 3 is a schematic block diagram of an embodiment of a dispersedstorage (DS) processing module 34 of user device 12 and/or of the DSprocessing unit 16. The DS processing module 34 includes a gatewaymodule 78, an access module 80, a grid module 82, and a storage module84. The DS processing module 34 may also include an interface 30 and theDSnet interface 32 or the interfaces 68 and/or 70 may be part of user 12or of the DS processing unit 14. The DS processing module 34 may furtherinclude a bypass/feedback path between the storage module 84 to thegateway module 78.

In an example of storing data, the gateway module 78 receives anincoming data object (e.g., a data file, a data block, an EC data slice,etc.) that includes a user ID field 86, an object name field 88, and thedata field 40. The gateway module 78 authenticates the user associatedwith the data object by verifying the user ID 86 with the managing unit18 and/or another authenticating unit. When the user is authenticated,the gateway module 78 obtains user information from the management unit18, the user device, and/or the other authenticating unit. The userinformation includes a vault identifier, operational parameters, anduser attributes (e.g., user data, billing information, etc.). A vaultidentifier identifies a vault, which is a virtual memory space that mapsto a set of DS storage units 36. For example, vault 1 (i.e., user 1'sDSN memory space) includes eight DS storage units (X=8 wide) and vault 2(i.e., user 2's DSN memory space) includes sixteen DS storage units(X=16 wide). The operational parameters may include an error codingalgorithm, the width n (number of pillars X or slices per segment forthis vault), a read threshold T, an encryption algorithm, a slicingparameter, a compression algorithm, an integrity check method, cachingsettings, parallelism settings, and/or other parameters that may be usedto access the DSN memory layer.

The gateway module uses the user information to assign a source name tothe data. For instance, the gateway module 60 determines the source nameof the data object 40 based on the vault identifier and the data object.For example, the source name may contain a data name (block number or afile number), the vault generation number, the reserved field, and thevault identifier. The data name may be randomly assigned but isassociated with the user data object.

The access module 62 receives the data object 40 and creates a series ofdata segments 1 through Y 90-92 therefrom. The number of segments Y maybe chosen or randomly assigned based on a selected segment size and thesize of the data object. For example, if the number of segments ischosen to be a fixed number, then the size of the segments varies as afunction of the size of the data object. For instance, if the dataobject is an image file of 4,194,304 eight bit bytes (e.g., 33,554,432bits) and the number of segments Y=131,072, then each segment is 256bits or 32 bytes. As another example, if segment sized is fixed, thenthe number of segments Y varies based on the size of data object. Forinstance, if the data object is an image file of 4,194,304 bytes and thefixed size of each segment is 4,096 bytes, the then number of segmentsY=1,024. Note that each segment is associated with the source name.

The grid module 82 may pre-manipulate (e.g., compression, encryption,cyclic redundancy check (CRC), etc.) each of the data segments beforeperforming an error coding function of the error coding dispersalstorage function to produce a pre-manipulated data segment. The gridmodule 82 then error encodes (e.g., Reed-Solomon, Convolution encoding,Trellis encoding, etc.) the data segment or pre-manipulated data segmentinto X error coded data slices 42-44. The grid module 64 determines aunique slice name for each error coded data slice and attaches it to thedata slice.

The value X, or the number of pillars (e.g., X=16), is chosen as aparameter of the error coding dispersal storage function. Otherparameters of the error coding dispersal function include a readthreshold T, a write threshold W, etc. The read threshold (e.g., T=10,when X=16) corresponds to the minimum number of error-free error codeddata slices required to reconstruct the data segment. In other words,the DS processing module 34 can compensate for X-T (e.g., 16−10=6)missing error coded data slices per data segment. The write threshold Wcorresponds to a minimum number of DS storage units that acknowledgeproper storage of their respective data slices before the DS processingmodule indicates proper storage of the encoded data segment. Note thatthe write threshold is greater than or equal to the read threshold for agiven number of pillars (X).

The grid module 82 also determines which of the DS storage units 36 willstore the EC data slices based on a dispersed storage memory mappingassociated with the user's vault and/or DS storage unit 36 attributes.The DS storage unit attributes includes availability, self-selection,performance history, link speed, link latency, ownership, available DSNmemory, domain, cost, a prioritization scheme, a centralized selectionmessage from another source, a lookup table, data ownership, and/or anyother factor to optimize the operation of the computing system. Notethat the number of DS storage units 36 is equal to or greater than thenumber of pillars (e.g., X) so that no more than one error coded dataslice of the same data segment is stored on the same DS storage unit 36.Further note that EC data slices of the same pillar number but ofdifferent segments (e.g., EC data slice 1 of data segment 1 and EC dataslice 1 of data segment 2) may be stored on the same or different DSstorage units 36.

The storage module 84 performs an integrity check on the EC data slicesand, when successful, transmits the EC data slices 1 through X of eachsegment 1 through Y to the DS Storage units. Each of the DS storageunits 36 stores its EC data slice and keeps a table to convert thevirtual DSN address of the EC data slice into physical storageaddresses.

In an example of a read operation, the user device 12 and/or 14 sends aread request to the DS processing unit 14, which authenticates therequest. When the request is authentic, the DS processing unit 14 sendsa read message to each of the DS storage units 36 storing slices of thedata object being read. The slices are received via the DSnet interface32 and processed by the storage module 84, which performs a parity checkand provides the slices to the grid module 82 when the parity check wassuccessful. The grid module 82 decodes the slices in accordance with theerror coding dispersal storage function to reconstruct the data segment.The access module 80 reconstructs the data object from the data segmentsand the gateway module 78 formats the data object for transmission tothe user device.

FIG. 4 is a schematic block diagram of an embodiment of a grid module 82that includes a control unit 73, a pre-data manipulator 75, an encoder77, a slicer 79, a post-data manipulator 81, a pre-data de-manipulator83, a decoder 85, a de-slicer 87, and/or a post-data de-manipulator 89.Note that the control unit 73 may be partially or completely external tothe grid module 82. For example, the control unit 73 may be part of thecomputing core at a remote location, part of a user device, part of theDS managing unit 18, or distributed amongst one or more DS storageunits.

In an example of write operation, the pre-data manipulator 75 receives adata segment 90-92 and a write instruction from an authorized userdevice. The pre-data manipulator 75 determines if pre-manipulation ofthe data segment 90-92 is required and, if so, what type. The pre-datamanipulator 75 may make the determination independently or based oninstructions from the control unit 73, where the determination is baseda computing system-wide predetermination, a table lookup, vaultparameters associated with the user identification, the type of data,security requirements, available DSN memory, performance requirements,and/or other metadata.

Once a positive determination is made, the pre-data manipulator 75manipulates the data segment 90-92 in accordance with the type ofmanipulation. For example, the type of manipulation may be compression(e.g., Lempel-Ziv-Welch, Huffman, Golomb, fractal, wavelet, etc.),signatures (e.g., Digital Signature Algorithm (DSA), Elliptic Curve DSA,Secure Hash Algorithm, etc.), watermarking, tagging, encryption (e.g.,Data Encryption Standard, Advanced Encryption Standard, etc.), addingmetadata (e.g., time/date stamping, user information, file type, etc.),cyclic redundancy check (e.g., CRC32), and/or other data manipulationsto produce the pre-manipulated data segment.

The encoder 77 encodes the pre-manipulated data segment 92 using aforward error correction (FEC) encoder (and/or other type of erasurecoding and/or error coding) to produce an encoded data segment 94. Theencoder 77 determines which forward error correction algorithm to usebased on a predetermination associated with the user's vault, a timebased algorithm, user direction, DS managing unit direction, controlunit direction, as a function of the data type, as a function of thedata segment 92 metadata, and/or any other factor to determine algorithmtype. The forward error correction algorithm may be Golay,Multidimensional parity, Reed-Solomon, Hamming, Bose Ray ChauduriHocquenghem (BCH), Cauchy-Reed-Solomon, or any other FEC encoder. Notethat the encoder 77 may use a different encoding algorithm for each datasegment 92, the same encoding algorithm for the data segments 92 of adata object, or a combination thereof.

The encoded data segment 94 is of greater size than the data segment 92by the overhead rate of the encoding algorithm by a factor of d*(X/T),where d is size of the data segment 92, X is the width or number ofslices, and T is the read threshold. In this regard, the correspondingdecoding process can accommodate at most X-T missing EC data slices andstill recreate the data segment 92. For example, if X=16 and T=10, thenthe data segment 92 will be recoverable as long as 10 or more EC dataslices per segment are not corrupted.

The slicer 79 transforms the encoded data segment 94 into EC data slicesin accordance with the slicing parameter from the vault for this userand/or data segment 92. For example, if the slicing parameter is X=16,then the slicer slices each encoded data segment 94 into 16 encodedslices.

The post-data manipulator 81 performs, if enabled, post-manipulation onthe encoded slices to produce the EC data slices. If enabled, thepost-data manipulator 81 determines the type of post-manipulation, whichmay be based on a computing system-wide predetermination, parameters inthe vault for this user, a table lookup, the user identification, thetype of data, security requirements, available DSN memory, performancerequirements, control unit directed, and/or other metadata. Note thatthe type of post-data manipulation may include slice level compression,signatures, encryption, CRC, addressing, watermarking, tagging, addingmetadata, and/or other manipulation to improve the effectiveness of thecomputing system.

In an example of a read operation, the post-data de-manipulator 89receives at least a read threshold number of EC data slices and performsthe inverse function of the post-data manipulator 81 to produce aplurality of encoded slices. The de-slicer 87 de-slices the encodedslices to produce an encoded data segment 94. The decoder 85 performsthe inverse function of the encoder 77 to recapture the data segment90-92. The pre-data de-manipulator 83 performs the inverse function ofthe pre-data manipulator 75 to recapture the data segment.

FIG. 5 is a diagram of an example of slicing an encoded data segment 94by the slicer 79. In this example, the encoded data segment includesthirty-two bits, but may include more or less bits. The slicer 79disperses the bits of the encoded data segment 94 across the EC dataslices in a pattern as shown. As such, each EC data slice does notinclude consecutive bits of the data segment 94 reducing the impact ofconsecutive bit failures on data recovery. For example, if EC data slice2 (which includes bits 1, 5, 9, 13, 17, 25, and 29) is unavailable(e.g., lost, inaccessible, or corrupted), the data segment can bereconstructed from the other EC data slices (e.g., 1, 3 and 4 for a readthreshold of 3 and a width of 4).

FIG. 6 is a schematic block diagram of the DS processing module 34operably coupled (e.g., via one or more networks) to a plurality of DSN(dispersed storage network) memory sites (e.g., DSN memory 1, a DSNmemory 2, and a DSN memory 3) of the DSN memory 22. In this example, DSNmemory site 1 includes one or more DS units 95-96 utilizing a memory A;DSN memory site 2 includes at least one DS unit 98 utilizing the memoryA and at least one DS unit utilizing a memory B 100; and DSN memory site3 includes at least one DS unit 102-104 utilizing the memory A and thememory B. Memory A and memory B have different memory characteristics,which are known to the DS processing module 34 and/or to the DS units95-104. The memory characteristics may include speed of access, cost,reliability, availability, capacity and other parameters. Note that DSunits 95-104 correspond to DS units 36 of FIG. 1.

In an example of operation, the DS processing module 34 has a dataobject to store and determines (e.g., looks up, receives, retrieves frommemory, etc.) storage metadata for the data object. The storage metadataincludes storage requirements for the data object. The storagerequirements include one or more of: a file type, file size, priority,security index, estimated storage time, estimated time betweenretrievals and more.

The DS processing module 34 then determines (e.g., looks up, receives,retrieves from memory, etc.) memory device capabilities of the DSNmemory 22. The memory device capabilities include a memory devicestorage cost, a memory device storage access speed, a memory devicestorage reliability, a memory device storage availability, and/or amemory device storage capacity. In this example, memory A has differentmemory device capabilities than memory B. For example, memory B may havea faster access speed than memory A.

The DS processing module 34 then identifies memory devices of the DSNmemory based on the memory device capabilities and the storage metadatato produce identified memory devices. For example, the DS processingmodule 34 interprets the storage requirements of the metadata andattempts to match the requirements with the memory device capabilities.As a specific example, if the data object has a storage requirement fora fast access time, then the DS processing module would identify memoryB for storage (as opposed to memory A in this example, which has aslower access time).

The DS processing module then encodes the data into a plurality of dataslices in accordance with an error coding dispersal function and outputsthe data slices to the identified memory devices for storage. Forexample, the slices are outputted to DS units 100-104 for storage inmemory B.

In another example of operation, the DS processing unit 16 considersmoving the previously stored data object and may choose to move the dataobject slices from one memory type to another (e.g., from memory B tomemory A). In this instance, the DS processing module 34 interprets thestorage metadata, which indicates that a fast data retrieval is nolonger required, and initiates the data transfer. The data transfer maybe a straight transfer of the data slices from memory B to memory A, ormay be done by reconstructing the data object from the slices in memoryB, re-encode the reconstructed data object using the same or differentoperational parameters of the error coding dispersal storage function toproduce re-constructed slices, and storing the reconstructed slices inmemory A.

FIG. 7 is a flowchart illustrating the determination of a datadistribution method where the DS processing unit may choose the memory,create the slices, and send the slices for storage to the chosen memory.The method begins at step 106 where the DS processing module receives adata object from a source (e.g., a user device, the storage integrityprocessing unit, another DS processing unit, the DS unit, and/or the DSmanaging unit).

The method continues at step 108 where the DS processing moduledetermines the storage metadata (e.g., a file type, file size, priority,security index, estimated storage time, estimated time betweenretrievals, etc.) associated with the data object. Such a determinationis based on one or more of the data, information received with the data,information derived from generation of the data, a command, a message,and/or a predetermination. Alternatively, or in addition to, thedetermination may be based on segmenting the data in accordance with anerror coding dispersal function to produce a plurality of data segmentsfollowed by subsequent determination of the storage metadata based on atleast one of the plurality of data segments. As yet another alternativeor addition, the determination may be based on partitioning the databased on customized data content (e.g., user preferences and/or files)and generic data content (e.g., a commonly available application) toproduce a customized data partition and a generic data partitionfollowed by the subsequent determination of customized data partitionstorage metadata regarding the customized data partition and genericdata partition storage metadata regarding the generic data partitionfollowed by aggregation of the customized data partition storagemetadata and the generic data partition storage metadata to produce thestorage metadata.

The method continues at step 110 where the DS processing unit determinesa storage dispersal method (e.g., operational parameters for an errorcoding dispersal storage function). The operational parameters includeone or more of: a pillar width, a read threshold, an error codingalgorithm, an encryption algorithm, a slicing parameter, a compressionalgorithm, an integrity check method, a caching settings, and aparallelism settings. Within step 110, the DS processing module encodesthe data segment in accordance with the storage dispersal method toproduce a plurality of error coded data slices (which may also bereferred to as data slices or slices). For example, the metadata mayrequire high reliability and fast retrieval speeds for a near term timeperiod. In this example, the DS processing unit would select a storagedispersal method to include a low number pillars (e.g., X) using acertain type of memory device to speed subsequent retrieval.

The method continues at step 112 where the DS processing moduledetermines a storage mode based on the metadata and memory capabilitiesof the DSN memory. The storage mode includes a memory selection and mayfurther include a time phase indicator. The time phase indicatorspecifies one or more time intervals for a given set of storagerequirements. For example, the time phase indicator specifies a firsttime phase that corresponds to a time period from the initial storage ofthe new data object and second time phase that corresponds to the timeperiod after the first time phase expires. As a specific example, the DSprocessing unit determines the storage mode to be a B mode (e.g., fastreliable and costly solid state memory) for the first time phase andstorage mode A for the second time phase.

The DS processing module may also determine the storage mode based onthe type of data. For example, the data may include customized datacontent (e.g., user preferences and/or files) and/or generic datacontent (e.g., a commonly available application). In this example, thegeneric data content may have one type of storage mode (e.g., slower,less reliable, etc.), while the customized data content may have anothertype of storage mode (e.g., faster, more reliable, etc.).

The method continues at step 114 where the DS processing unit utilizesthe current storage mode to store slices in the DSN memory. In thisinstance, the DS processing unit looks up the mapping in the virtual DSNaddress to physical location table to determine where the slices shouldbe stored. Note that the virtual DSN address to physical location tablemay include both the current storage mode and the last storage mode tofacilitate moving slices from the memory of the last mode to the memoryin accordance with the current storage mode.

When the storage mode is mode B, the method continues to step 116 wherethe DS processing module sends the data slices to DS units with memorytype B. When the storage mode is mode A, the method continues to step122 where the DS processing sends the data slices to DS units withmemory type A. Note that such decisions may be made on a data segment bydata segment basis or for groupings of data segments (e.g., a datafile).

When the storage mode is mode A/B, the method continues at step 118where the DS processing module sends k slices to DS units with memorytype B 118 and, at step 120, sends the other n-k slices to DS units withmemory type A. Note that this scenario may include themetadata-indicated requirement for fast access (without failures),reliable memory with some cost constraint for the current time phase.Further note that when k is equal to or is greater than the readthreshold, the DS processing unit can retrieve slices from the memory Bwithout retrieving slices from memory A unless one or more slices frommemory B is missing or corrupt.

After storing the slices, the method continues at step 124 where the DSprocessing module determines whether it is time to reassess the storagemode. Such a determination may be based on one or more of a time periodhas elapsed since the current storage mode, there have been noretrievals of the data object within a time period, a command, arequest, and/or a memory type is filling up (e.g., memory B). Note thata likely scenario is starting with the B mode (e.g., fast and frequentdata retrievals), transition to the A/B mode (e.g., less frequent, butstill fast data retrievals), and then transition and remain at in mode A(e.g., less frequent and slower data retrievals).

Alternatively, or in addition to, the reassessing may be based on theoccurrence of a condition to update the identification of the memorydevices. The condition may include one or more of, but not limited to,updating of the storage metadata, a change of memory devicecharacteristics, a change of available memory devices, and/or anoccurrence of a triggering event. For example, the processing module maydetermine that the condition has occurred to update the dedication ofthe memory devices when new memory devices with more favorable memorycharacteristics relative to the storage requirements are available. Themethod continues with the step where the processing module re-identifiesmemory devices when the condition has occurred. In such an instance, theprocessing module may retrieve a portion of the plurality of data slicesand facilitate moving the plurality of data slices to the re-identifiedmemory devices.

If not reassessing, the method repeats at step 114. If reassessing, themethod continues step 112 where the DS processing unit determineswhether to change the storage mode. Such a change may be to move fromstorage mode B to storage mode A/B or to storage mode A. Other changesof the storage mode may also be determined, such as to change anoperational parameter of the error coding dispersal storage function(e.g., number of pillars), which would revert the method to step 110.

FIG. 8 is a flowchart illustrating a method that begins at step 126where the DS processing module receives a data object from a source(e.g., a user device, the storage integrity processing unit, another DSprocessing unit, the DS unit, or the DS managing unit). The methodcontinues at step 128 where the DS processing module determines metadataassociated with the data object, which may be done in a similar manneras discussed with reference to step 108 of FIG. 7.

The method continues at step 130 where the DS processing moduledetermines a first dispersal method in a manner similar to step 110 ofFIG. 7. In addition, the DS processing module determines to store theslices in a DS units having a first type of memory (e.g., memory havinga first set of memory capabilities). The method continues at step 132where the DS processing module sends the slices to the DS units with thefirst memory type.

The method continues at step 134 where the DS processing unit determineswhether it is time to move the slices from the first type of memorydevice to a second type of memory device. Such a determination may bebased on one or more of, but not limited to, an elapsed time period ofstorage in the first type of memory, an elapsed time period since a dataslice retrieval from the first type of memory, a first type of memoryutilization indicator, a command, and/or a request. For example, theprocessing module may determine to transfer the plurality of data sliceswhen the processing module determines that the elapsed time period ofstorage in the first type of memory exceeds a storage threshold.

The method repeats at step 134 when it is not time to move the slices.When it is time to move the slices, the method continues at step 136where the DS processing module retrieves the slices from the DS unitshaving memory of the first memory type. The method then continues atstep 137 where the DS processing module determines whether toreconstruct data from the data slices. Such a determination may be basedon the type of data, the second memory type, a change in the storagerequirements (e.g., archiving, reduced retrieval needs, etc.), change inthe operational parameters of the error coding dispersal storagefunction, and/or any other factor that would require the data to bereconstructed.

When the data is to be reconstructed, the method continues at step 138the DS processing module reconstructs at least a portion of the datafrom the plurality of data slices in accordance with a first errorcoding dispersal function to produce reconstructed data. The first errorcoding dispersal function includes one or more of but not limited to anerror coding type that includes at least one of an error codingalgorithm, an encryption algorithm, and a compression algorithm andoperational parameters that include two or more of a pillar width, aread threshold, a slicing parameter, an integrity check method, acaching settings, and a parallelism settings.

The method continues to step 139 where the DS processing moduledetermines a second dispersal method (e.g., a second error codingdispersal storage function and identify the DS units having memory ofthe second type). The second error coding dispersal function includesone or more of, but not limited to, an error coding type that includesat least one of an error coding algorithm, an encryption algorithm, anda compression algorithm and operational parameters that include two ormore of a pillar width, a read threshold, a slicing parameter, anintegrity check method, a caching settings, and a parallelism settings.In an example, the second error coding dispersal function may includethe error coding type that is substantially the same as the error codingtype of the first error coding dispersal function. In another example,the second error coding dispersal function may include a different errorcoding type than that of the first error coding dispersal function. Inyet another example, the second error coding dispersal function mayinclude operational parameters that are substantially the same as theoperational parameters of the first error coding dispersal function. Infurther example, the second error coding dispersal function may includedifferent operational parameters than that of the first error codingdispersal function.

The method continues to step 140 where the DS processing module encodesthe reconstructed data into a second plurality of slices in accordancewith the second error coding dispersal storage function. The methodcontinues at step 142 from step 140 (or from step 137 when the data isnot to be reconstructed) where the DS processing module sends the slices(e.g., the original ones or the new ones) to DS units having memory ofthe second type. The method continues at step 144 where the DSprocessing module updates the virtual DSN address to physical locationtable to reflect where the slices are now stored. Note that the methodof FIG. 8 may be applied on a data segment by data segment basis or forgroup of data segments (e.g., a data file). In the latter case,pluralities of data slices may be processed to reconstruct the data(e.g., reconstruct the data file) and then the reconstructed data (e.g.,data file) is encoded to produce pluralities of slices encoded inaccordance with the second error coding dispersal storage function.

FIG. 9 is a schematic block diagram of an embodiment of a distributedstorage unit 146 (e.g., DS unit 36 &/or 95-104) that includes a storageunit control module 148, a plurality of memories of type A (1 througha), and a plurality of memories of type B (1 through b). The storageunit control module 148 includes the DSnet interface 150, an internalmemory for DS tables and logs 152, a memory for the operating system(OS) 154, and the DS processing 156. The storage unit control module 148may be operably coupled to the computing system via the DSnet interface150 via the network.

The memories may be implemented as memory devices that are included inthe DS storage unit 146 and/or outside of the DS storage unit 146. Thememory devices may include but not limited to one or more of a magnetichard disk, NAND flash, read only memory, optical disk, and/or any othertype of read-only, and/or read/write memory. For example, memory A-1 maybe implemented in the DS unit 146 and memory A-2 may be implemented in aremote server (e.g., a different DS unit operably coupled to the DS unit146 via the network). In an example, memory A-1 through memory A-a areimplemented with the magnetic hard disk technology and memory B-1through memory B-b are implemented with the NAND flash technology. Thememory devices may be associated with one or more memory device storagecharacteristics. Memory device storage characteristics may include oneor more of but not limited to a memory device storage cost, a memorydevice storage access speed, memory device storage reliability, memorydevice storage availability, and/or a memory device storage capacity.The memory devices may further comprise main memory 54, a local non-mainmemory, and/or a non-local non-main memory 36.

The DS tables and logs memory 152 may be utilized to store operationaldata. The DS unit operational data may include one or more of but notlimited to a DS table, a local virtual distributed storage network (DSN)address to physical memory table, a log, an activity record, a memoryutilization record, an error record, a storage record, a retrievalrecord, and/or a vault information record. In other words, the DS unitoperational data may be data that is used from time to time to operatethe DS unit. The operating system memory 154 may be utilized to store aDS unit operating system algorithm. The DS unit operating systemalgorithm may include at least a portion of operating system executablesoftware that is utilized to operate the DS unit.

In an example of a write operation, the DS processing of the DS unitreceives an encoded slice to store. For example, the DS unit may receivean encoded slice from a user device for storage in the DS unit. Themethod begins with the step where the DS processing determines if the DSunit operating system is running. The method branches to the step wherethe DS processing selects one of the plurality of memory devices forstoring the encoded slice when the DS processing determines that the DSunit operating system is running. The DS processing may retrieve slicesof at least a portion of the operating system from one or more of thememories when the DS processing determines that the operating system isnot running. The DS processing may decode the retrieved slices of the atleast a portion of the operating system in preparation for execution asrequired.

The method continues with the step where the DS processing selects oneof the plurality of memory devices for storing the encoded slice toproduce a selected memory device based on one or more of but not limitedto metadata associated with the encoded slice and a memory-based storagemode. The memory-based storage mode may include the memory selection anda time phase indicator. Such a selection may be based on one or more ofthe metadata, a command (e.g., from the DS processing unit indicatingwhich memory type to use), a type of data indicator, a priorityindicator, available memory, memory performance data, memory cost data,and/or any other parameter to facilitate desired levels of efficiencyand performance. For example, the storage unit control module 148 maychoose memory A-1 (e.g., a magnetic hard disk drive) to store thereceived EC data slice since the performance and efficiency is goodenough for the EC data slice requirements (e.g., availability, cost,response time). In another example, the storage unit control module 148distributes slices across the DS unit memories. In another example, thestorage unit control module 148 distributes a read threshold k of theslices across memory B (for fast retrieval) and the other n-k slicesacross memory A. In yet another example, the storage unit control module148 distributes the slices across the DS unit memories and at least oneother DS unit at the same site as the DS unit 146. In yet anotherexample, the storage unit control module 148 distributes the slicesacross the DS unit memories and at least one other DS unit at adifferent site as the DS unit 146.

The DS processing may determine if the operational data memory 152 isavailable. The DS processing may utilize the operational data from theoperational data memory 152 when the DS processing determines that theoperational data memory 152 is available. In an alternative, the DSprocessing may select one of the memory devices of the DS unit byretrieving data slices of the DS unit operational data from the memorydevices to produce retrieved data slices when the DS processingdetermines that the operational data memory 152 is not available. The DSprocessing reconstructs vault information from the retrieved data slicesin accordance with the error coding dispersal storage function. The DSprocessing selects one of the memory devices based on the vaultinformation. In other words, the DS processing retrieves operationaldata to determine where to store the encoded slice. DS processing mayupdate the operational data to produce updated operational data. The DSprocessing may encode the updated operational data to produce updatedvault information data slices in accordance with the error codingdispersal storage function. The DS processing may store the updatedvault information data slices in the memory devices. The DS processingof the DS unit stores the received encoded slice in the selected memorydevice. The DS processing may change the status of the operational datamemory 152 to unavailable. The DS processing may deactivate the DS unitoperating system and/or the operating system memory 154.

In an example of a read operation, the DS processing receives a readrequest for an encoded data slice. The method begins with the step wherethe DS processing determines if the DS unit operating system is running.The method branches to the step where the DS processing determines ifthe operational data memory 152 is available when the DS processingdetermines that the DS unit operating system is running.

The method continues with the step where the DS processing determines ifthe operational data memory 152 is available. The DS processing mayretrieve slices of at least a portion of the operating system from oneor more of the memories when the DS processing determines that theoperating system is not running. The DS processing may decode theretrieved slices of the at least a portion of the operating system inpreparation for execution as required.

The method continues with the step where the DS processing may determineif the operational data memory 152 is available. The DS processing mayutilize the operational data (e.g., which memory device contains theencoded data slice to be retrieved) from the operational data memory 152when the DS processing determines that the operational data memory 152is available. The DS processing may select one of the memory devices ofthe DS unit where the encoded data slices stored by retrieving dataslices of the DS unit operational data from the memory devices toproduce retrieved data slices when the DS processing determines that theoperational data memory 152 is not available. The DS processingreconstructs vault information from the retrieved data slices inaccordance with the error coding dispersal storage function. The DSprocessing selects one of the memory devices based on the vaultinformation. In other words, the DS processing retrieves operationaldata to determine where to retrieve the encoded slice.

The method continues with the step where the DS processing determineswhich memory device contains the encoded data slice to be retrievedbased on the operational data. The DS processing retrieves the encodeddata slice from the selected memory device. The DS processing outputsthe encoded data slice to the requester via the DSnet interface 150. TheDS processing may change the status of the operational data memory 152to unavailable. The DS processing may deactivate the DS unit operatingsystem and/or the operating system memory 154.

In an example of a slice transfer operation, the DS processing receivesa request to transfer a slice from a first memory type to a secondmemory type. The method begins with the step where the DS processingdetermines if the DS unit operating system is running. The methodbranches to the step where the DS processing determines if theoperational data memory 152 is available when the DS processingdetermines that the DS unit operating system is running.

The method continues with the step where the DS processing determines ifthe operational data memory 152 is available. The DS processing mayretrieve slices of at least a portion of the operating system from oneor more of the memories when the DS processing determines that theoperating system is not running. The DS processing may decode theretrieved slices of the at least a portion of the operating system inpreparation for execution as required.

The method continues with the step where the DS processing may determineif the operational data memory 152 is available. The DS processing mayutilize the operational data (e.g., which memory device contains theencoded data slice to be transferred) from the operational data memory152 when the DS processing determines that the operational data memory152 is available. The DS processing may select one of the memory devicesof the DS unit where the encoded data slices are stored by retrievingdata slices of the DS unit operational data from the memory devices toproduce retrieved data slices when the DS processing determines that theoperational data memory 152 is not available. The DS processingreconstructs vault information from the retrieved data slices inaccordance with the error coding dispersal storage function. The DSprocessing selects one of the memory devices based on the vaultinformation. In other words, the DS processing retrieves operationaldata to determine where to retrieve the encoded slice.

The method continues with the step where the DS processing determineswhich memory device contains the encoded data slice to be retrievedbased on the operational data. The DS processing retrieves the encodeddata slice from the selected memory device. The DS processing determineswhich memory to transfer the encoded data slice to in response to therequester transfer. The determination may be based on one or more of atime period has expired since the last store, a command, an errormessage, a change in the memory architecture (e.g., a new memory deviceis added), and/or at least one of the DS tables, logs, and OS havechanged. Having determined where to store the slice, the DS processingstores the slice in the selected memory. The DS processing updates andmaintains a local virtual DSN address to physical memory table as partof the DS tables 152. The table maintains a record of where the slicesare physically stored in the memories and associated the physicallocation to the slice name. The DS processing may change the status ofthe operational data memory 152 to unavailable. The DS processing maydeactivate the DS unit operating system and/or the operating systemmemory 154.

Note that the storage unit control module 148 may utilize the DSprocessing 156 to distributedly store the DS tables, logs, and OS (e.g.,that also utilize internal memory of the storage unit control module148) to improve the reliability of operation of the DS unit 146. The DSunit 146 may subsequently retrieve and restore one or more of the DStables, logs, and OS. The storage unit control module 148 may determinewhen to distributedly store one or more of the DS tables, logs, and OS.

FIG. 10 is a flowchart illustrating the determination of a data storagemethod where a DS processing module of a DS unit may choose a memory tostore a new slice and/or subsequently move a slice.

The method begins at step 158 where the DS processing module receives,via an interface module 150, an encoded data slice and metadata from asource (e.g., a user device, the storage integrity processing unit, theDS processing unit, another DS unit, and/or the DS managing unit 158).The DS processing unit (e.g., or another unit with DS processing)created the metadata associated with the data object as previouslydiscussed with reference to FIG. 7.

The method continues at step 160 where the DS processing moduledetermines the memory requirements based on the metadata. For example,the metadata may indicate a very high reliability requirement and a fastretrieval speed requirement for a near term time period. The DSprocessing module may subsequently choose the memory device that bestmatches the requirements.

The method continues at step 162 where the DS processing moduledetermines memory availability. The determination may be based on one ormore of but not limited to a query, a command, a message, and errormessage, and/or a table lookup. In an instance, the DS processing modulemay retrieve a plurality of data slices from at least some of theplurality of memory devices based on the encoded slice. In other words,the DS processing module retrieves the plurality of data slices that areassociated with the encoded slice such as a vault identity. The DSprocessing module reconstructs DS operational data from the plurality ofdata slices in accordance with an error coding dispersal storagefunction. The DS operational data may include one or more of but notlimited to a DS table, a local virtual distributed storage network (DSN)address to physical memory table, a log, an activity record, a memoryutilization record, an error record, a storage record, a retrievalrecord, a vault information record. Within step 162 the DS processingmodule may further determine memory characteristics based on retrievinginformation previously stored in DS tables.

The method continues at step 164 where the DS processing moduledetermines a storage mode based on the metadata and memory capabilitiesof the DS unit. The storage mode includes a memory selection and mayfurther include a time phase indicator. The time phase indicatorspecifies one or more time intervals for a given set of storagerequirements. For example, the time phase indicator specifies a firsttime phase that corresponds to a time period from the initial storage ofthe new data object and second time phase that corresponds to the timeperiod after the first time phase expires. As a specific example, the DSprocessing module determines the storage mode to be a B mode (e.g., fastreliable and costly solid state memory) for the first time phase andstorage mode A for the second time phase.

The DS processing module may also determine the storage mode based onthe type of data. For example, the data may include customized datacontent (e.g., user preferences and/or files) and/or generic datacontent (e.g., a commonly available application). In this example, thegeneric data content may have one type of storage mode (e.g., slower,less reliable, etc.), while the customized data content may have anothertype of storage mode (e.g., faster, more reliable, etc.).

The method continues at step 166 where the DS processing module utilizesthe current storage mode to store slices in the DS unit. In thisinstance, the DS processing module looks up the mapping in the DSoperational data (e.g., a local virtual DSN address to physical locationtable) to determine where the slice should be stored. Note that thevirtual DSN address to physical location table may include both thecurrent storage mode and the last storage mode to facilitate movingslices from the memory of the last mode to the memory in accordance withthe current storage mode.

When the storage mode is mode B, the method continues to step 166 wherethe DS processing module stores the data slice to a memory device withmemory type B. When the storage mode is mode A, the method continues tostep 174 where the DS processing stores the data slice to a memorydevice with memory type A. Note that such decisions may be made on adata segment by data segment basis or for groupings of data segments(e.g., a data file).

When the storage mode is mode A/B, the method continues at step 170where the DS processing module stores the data slice to the memorydevice with memory type B and, at step 172, stores the data slice to thememory device with memory type A. Note that this scenario may includethe metadata-indicated requirement for fast access (without failures)and reliable memory with some cost constraint for the current timephase. In other words, the data slice may be subsequently retrieved fromthe memory device of either memory type A or memory type B in accordancewith a requirement of the retrieval.

After storing the slices, the method continues at step 176 where the DSprocessing module determines whether it is time to reassess the storagemode. Such a determination may be based on one or more of a time periodhas elapsed since the current storage mode, there have been noretrievals of the data slice within a time period, a command, a request,and/or a memory type is filling up (e.g., memory B). Note that a likelyscenario is starting with the B mode (e.g., fast and frequent dataretrievals), transition to the A/B mode (e.g., less frequent, but stillfast data retrievals), and then transition and remain at in mode A(e.g., less frequent and slower data retrievals).

Alternatively, or in addition to, the reassessing may be based on theoccurrence of a condition to update the identification of the memorydevices. The condition may include one or more of, but not limited to,updating of the storage metadata, a change of memory devicecharacteristics, a change of available memory devices, and/or anoccurrence of a triggering event. For example, the DS processing modulemay determine that the condition has occurred to update theidentification of the memory devices when new memory devices with morefavorable memory characteristics relative to the storage requirementsare available. The method continues with the step where the processingmodule re-identifies memory devices when the condition has occurred. Insuch an instance, the processing module may retrieve data slice andfacilitate moving of the data slice to the re-identified memory device.

If not reassessing, the method repeats at step 166. If reassessing, themethod continues step 164 where the DS processing module determineswhether to change the storage mode. Such a change may be to move fromstorage mode B to storage mode A/B or to storage mode A.

FIG. 11 is a flowchart illustrating the management of a memory devicewhere the DS unit may power down a memory device that is not utilizedoften to extend the operational life of the memory device.

In an embodiment, the DS unit previously discussed with reference toFIG. 9 includes a plurality of memory devices. The plurality of memorydevices includes a first set of memory devices (e.g., memory devices A-1to A-a) that are continually active and a second set of memory devices(e.g., memory devices B-1 to B-b) that are selectively active. In aninstance, the first set of memory devices store first data having a rateof retrieval in a first interval retrieval rate range and the second setof memory devices store second data having a rate of retrieval in asecond interval retrieval rate range. For example, the first set ofmemory devices may be utilized when data is retrieved at a higher ratethan the data retrieved from the second set of memory devices. In aninstance, data is archived utilizing the second set of memory devicesfollowed such that at least one memory device of the second set ofmemory devices may be de-activated from time to time. Note that thede-activation of a memory device may provide the system with areliability improvement and/or power savings.

In an example of a store operation, the method begins with step 178where the DS processing module 156 of the DS unit 146 receives anencoded slice and metadata from a source (e.g., a user device, thestorage integrity processing unit, the DS processing unit, another DSunit, or the DS managing unit). The DS processing unit (e.g., or anotherunit with DS processing) created the metadata associated with the dataobject as previously discussed.

The method continues with step 180 where the DS processing moduledetermines memory requirements as discussed with reference to step 160of FIG. 10. For example, the metadata may indicate a very highreliability requirement and a fast retrieval speed requirement for thenear term time period. In another example, the metadata may indicate avery long period of storage with few retrievals requirement (e.g.,records archive). The DS processing module may subsequently choose thememory that best matches those requirements as described below.

The method continues with step 182 where the DS processing moduledetermines memory availability as discussed with reference to step 162of FIG. 10. The method continues with step 184 where the DS processingmodule determines the storage mode based on one or more of but notlimited to the memory requirements, the memory availability, and/ormemory characteristics. The storage mode may include the memoryselection and a time phase indicator. The time phase may include a firstphase to include the time period between the initial storage of the newslice until the time when the memory is to be powered off. Note thatother time phases may comprise a subsequent phase to include the timeperiod between the last power down until the time when the memory poweris to be turned back on to perform memory tests. For example, the DSprocessing module determines the storage mode to be a long term archiveafter a ten day first time phase after the initial slice storage whensubsequent retrievals may be frequent. The DS processing module mayupdate the local virtual DSN address to physical location table toreflect where the slice will be stored.

The method continues with step 186 where the DS processing module storesthe encoded slice in the one of the second set of memory device when theencoded slice is to be stored in the one of the second set of memorydevices. The DS processing module may de-activate the one of the secondset of memory devices, in accordance with a deactivation protocol, afterstoring the encoded slice. The deactivation protocol may include one ormore of but not limited to elapsed time since storing the encoded slicein the one of the second set of memory devices, elapsed time since aretrieval request for the encoded slice, elapsed active state time ofthe one of the second set of memory devices, a command, an irregularpower indicator, an earthquake indicator, a bad weather indicator, aretrieval frequency indicator, and/or an indicator to improve the lifeof the memory device.

In another embodiment, the DS processing module stores the encoded slicein the one of the first set of memory devices when the encoded slice isto be stored in the one of the first set of memory devices. The DSprocessing module may determine whether to transfer the encoded slicefrom the one of the first set of memory devices to the one of the secondset of memory devices based a data transfer protocol (e.g., how muchtime later, a condition of transfer etc.). For example, the processingunit may determine to transfer the encoded slice when a time period haselapsed its initial storage of the encoded slice in the one of the firstset of memory devices. The processing unit may retrieve the encodedslice from the one of the first set of memory devices and store theencoded slice in the one of the second set of memories when theprocessing unit determines that the encoded slice is to be transferred.

The method continues with step 188 where the DS processing moduledetermines when to de-activate (e.g., turn off) the memory device toproduce a de-activated memory device. The determination may be based onone or more of but not limited to elapsed time since a retrieval requestfor at least a portion of the second data, elapsed time since a storerequest for at least a portion of the second data, elapsed active statetime of the memory device, a command, an irregular power indicator, anearthquake indicator, a bad weather indicator, a retrieval frequencyindicator, and/or an indicator to improve the life of the memory device.If not turning off the memory, the method repeats at step 188. Ifturning off the memory, the method continues to step 189 where the DSprocessing module turns off the memory.

The method continues with step 190 where the DS processing moduledetermines when to activate (e.g., turn on) the memory. The DSprocessing module determines when to activate the memory device (e.g.,of the second set) based on one or more of but not limited to aretrieval request for at least a portion of the second data, elapsedinactive state time of the memory device of the second set, a command,an irregular power indicator, an earthquake indicator, a bad weatherindicator, a retrieval frequency indicator, and/or an indicator toimprove the life of the memory device. Note that the memory may beactivated to perform integrity and consistency checks of the storedslices. If not turning on the memory, the method repeats at step 190. Ifturning on the memory, the method continues to step 191 where the DSprocessing module turns on the memory. The DS processing module mayretrieve the encoded slice and/or slice information from the activatedmemory device. The slice information may include one or more of but notlimited to an encoded slice, content data, error control information, ahash of a slice name list, a slice name list, a source name list, a hashof a source name list, and/or a slice revision.

The method continues with step 192 where the DS processing moduledetermines whether the retrieved encoded slice has an error (e.g.,failed memory or slice inconsistency). The determination may be based onone or more of but not limited to a missing slice test, an outdatedslice revision test, a slice name comparison to at least one other slicename from a slice name list, a slice revision comparison to at least oneother slice revision from a slice revision list, a slice name comparisonto at least one other slice name from another DS unit, a slice revisioncomparison to at least one other slice revision from another DS unit,and/or a stored checksum comparison to a re-calculated checksum.

The method returns to step 188 to determine when to turn the memory offwhen the DS processing module does not detect any errors. In thisinstance, the DS processing module may determine a condition for theprevious activation of the memory device when the retrieved encodedslice does not have an error. In other words, the DS processing moduledetermines why the memory device was activated (e.g., to check forerrors and/or to retrieve an encoded slice). The DS processing modulesends, via an interface module, the retrieved encoded slice andinitiates deactivation of the memory device when the condition was adata access request (e.g., to retrieve and encoded slice). The DSprocessing module initiates the deactivation of the memory device whenthe condition was verification-based (e.g., to check for errors).

The method continues to step 194 where the DS processing moduledetermines when to rebuild the slices with errors when the DS processingmodule detects errors. The rebuild determination may be based on one ormore of memory device availability (e.g., may be waiting for areplacement hard disk drive to be installed), a command, a timer, and/ora substitute memory becoming available. If not rebuilding, the methodrepeats at step 194. If rebuilding, the method continues to step 196where the DS processing module rebuilds and stores the recreated slice.The DS processing module retrieves good slices of the same segment fromthe other pillar DS units, de-slices, and decodes to produce theoriginal data object. The DS processing module recodes and re-slices theoriginal data object to produce repaired slices for the one or moreslices that were in error. The DS processing module stores the repairedslices in the DS unit memory and updates the local virtual DSN addressto physical location table if there are any changes (e.g., when asubstitute memory is utilized). The DS processing module may de-activatethe activated memory device (e.g., right away or on a delayed basis).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “coupled to” and/or “coupling” and/or includes direct couplingbetween items and/or indirect coupling between items via an interveningitem (e.g., an item includes, but is not limited to, a component, anelement, a circuit, and/or a module) where, for indirect coupling, theintervening item does not modify the information of a signal but mayadjust its current level, voltage level, and/or power level. As mayfurther be used herein, inferred coupling (i.e., where one element iscoupled to another element by inference) includes direct and indirectcoupling between two items in the same manner as “coupled to”. As mayeven further be used herein, the term “operable to” indicates that anitem includes one or more of power connections, input(s), output(s),etc., to perform one or more its corresponding functions and may furtherinclude inferred coupling to one or more other items. As may stillfurther be used herein, the term “associated with”, includes directand/or indirect coupling of separate items and/or one item beingembedded within another item. As may be used herein, the term “comparesfavorably”, indicates that a comparison between two or more items,signals, etc., provides a desired relationship. For example, when thedesired relationship is that signal 1 has a greater magnitude thansignal 2, a favorable comparison may be achieved when the magnitude ofsignal 1 is greater than that of signal 2 or when the magnitude ofsignal 2 is less than that of signal 1.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

1. A method for dispersed memory storage comprises: determining whetherto transfer a plurality of data slices from a first type of memorydevice to a second type of memory device; when the plurality of dataslices is to be transferred from the first type of memory device to thesecond type of memory device, determining whether to reconstruct datacorresponding to the plurality of data slices; when the data is to bereconstructed: retrieving the plurality of data slices from a first setof memory devices that are of the first type of memory; reconstructingat least a portion of the data from the plurality of data slices inaccordance with a first error coding dispersal function to producereconstructed data; encoding the reconstructed data in accordance with asecond error coding dispersal function to produce a second plurality ofdata slices; and storing the second plurality of data slices in a secondset of memory devices that are of the second type of memory.
 2. Themethod of claim 1, wherein the determining whether to transfer theplurality of data slices further comprises: determining whether totransfer a plurality of data slices based on at least one of: elapsedtime period of storage in the first type of memory; elapsed time periodsince a data slice retrieval from the first type of memory; a first typeof memory utilization indicator; receiving a command; and receiving arequest.
 3. The method of claim 1 further comprises: when the data isnot to be reconstructed: retrieving the plurality of data slices fromthe first set of memory devices that are of the first type of memory;storing the plurality of data slices in the second set of memory devicesthat are of the second type of memory; and facilitating deletion of theplurality of data slices from the first set of memory devices that areof the first type of memory.
 4. The method of claim 1, wherein the firsterror coding dispersal function comprises: an error coding type thatincludes at least one of an error coding algorithm, an encryptionalgorithm, and a compression algorithm; and operational parameters thatinclude two or more of a pillar width, a read threshold, a slicingparameter, an integrity check method, a caching settings, and aparallelism settings.
 5. The method of claim 1, wherein the second errorcoding dispersal function comprises: an error coding type that includesat least one of an error coding algorithm, an encryption algorithm, anda compression algorithm; and operational parameters that include two ormore of a pillar width, a read threshold, a slicing parameter, anintegrity check method, a caching settings, and a parallelism settings.6. The method of claim 1 further comprises: when the data is to bereconstructed: retrieving pluralities of data slices from the first setof memory devices, wherein each of the pluralities of data slicescorresponds to a data segment; reconstructing the data from thepluralities of data slices in accordance with a first error codingdispersal function to produce reconstructed data; encoding thereconstructed data in accordance with a second error coding dispersalfunction to produce a second pluralities of data slices; and storing thesecond pluralities of data slices in the second set of memory devices.7. The method of claim 1, wherein the at least a portion of the datacomprises: a data partition, wherein the data partition corresponds toat least one of: customized data content; and generic data content.
 8. Acomputer comprises: a dispersal memory interface; and a processingmodule operable to: determine whether to transfer a plurality of dataslices from a first type of memory device to a second type of memorydevice; when transferring the plurality of data slices from the firsttype of memory device to the second type of memory device, determinewhether to reconstruct data corresponding to the plurality of dataslices; when the data is to be reconstructed: retrieve, via thedispersal memory interface, the plurality of data slices from a firstset of memory devices that are of the first type of memory; reconstructat least a portion of the data from the plurality of data slices inaccordance with a first error coding dispersal function to producereconstructed data; encode the reconstructed data in accordance with asecond error coding dispersal function to produce a second plurality ofdata slices; and output, via the dispersal memory interface, the secondplurality of data slices to a second set of memory devices that are ofthe second type of memory.
 9. The computer of claim 8 further comprisesat least one of: a main memory; a local non-main memory; and a non-localnon-main memory.
 10. The computer of claim 8, wherein the dispersalmemory interface may comprise at least one of: a multi-general purposeinput output; and a plurality of interfaces.
 11. The computer of claim8, wherein the processing module determines whether to transfer aplurality of data slices by: determining whether to transfer a pluralityof data slices based on at least one of: elapsed time period of storagein the first type of memory; elapsed time period since a data sliceretrieval, via the dispersal memory interface, from the first type ofmemory; a first type of memory utilization indicator; obtaining acommand; and obtaining a request.
 12. The computer of claim 8, whereinthe processing module further functions to: when the data is not to bereconstructed: retrieving, via the dispersal memory interface, theplurality of data slices from the first set of memory devices that areof the first type of memory; outputting, via the dispersal memoryinterface, the plurality of data slices in the second set of memorydevices that are of the second type of memory; and facilitatingdeletion, via the dispersal memory interface, of the plurality of dataslices from the first set of memory devices that are of the first typeof memory.
 13. The computer of claim 8, wherein the first error codingdispersal function comprises: an error coding type that includes atleast one of an error coding algorithm, an encryption algorithm, and acompression algorithm; and operational parameters that include two ormore of a pillar width, a read threshold, a slicing parameter, anintegrity check method, a caching settings, and a parallelism settings.14. The computer of claim 8, wherein the second error coding dispersalfunction comprises: an error coding type that includes at least one ofan error coding algorithm, an encryption algorithm, and a compressionalgorithm; and operational parameters that include two or more of apillar width, a read threshold, a slicing parameter, an integrity checkmethod, a caching settings, and a parallelism settings.
 15. The computerof claim 8, wherein the processing module further functions to: when thedata is to be reconstructed: retrieving, via the dispersal memoryinterface, pluralities of data slices from the first set of memorydevices, wherein each of the pluralities of data slices corresponds to adata segment; reconstructing the data from the pluralities of dataslices in accordance with a first error coding dispersal function toproduce reconstructed data; encoding the reconstructed data inaccordance with a second error coding dispersal function to produce asecond pluralities of data slices; and outputting, via the dispersalmemory interface, the second pluralities of data slices to the secondset of memory devices.
 16. The computer of claim 8, wherein the at leasta portion of the data comprises: a data partition, wherein the datapartition corresponds to at least one of: customized data content; andgeneric data content.